With the reduction of the number of incandescent lamps together with the large-scale usage of fluorescent and light emitting diode（LED） lights at the same time， the deficiency of International Electrotechnical Commission（IEC） flickermeter that can not measure interharmonic-caused voltage flickers has become increasingly apparent. It is known that the display of measured sinusoidal waveforms is closer to the original signal if sine interpolation method is used. Clearly， the sine interpolation method is able to overcome the deficiencies associated with the IEC flickermeter.The principle of sine interpolation is analyzed in detail and it is found that the sine interpolation may lead to a wrong assessment on the flicker. The source of error in sine interpolation is analyzed and a new approach is proposed. This new approach deducts a constant before using the sine interpolation method to measure voltage flickers. The new approach can measure voltage flickers caused by both low-frequency and high-frequency interharmonics. The new approach promotes further study on flicker measuring algorithms.